What should you know about equine exertional rhabdomyolysis?

During an episode, muscle cells are injured after exertion and release substances into the bloodstream. A horse may become stiff, develop hard or painful muscles over the hindquarters, sweat heavily, or refuse to walk. Urine may look unusually dark, but normal-looking urine does not rule out a problem. The episode can resemble ordinary muscle soreness after exercise, yet the intensity, sudden onset, and difficulty moving make veterinary assessment essential.

Stop exercise and keep the horse calm in a safe place. Do not force walking, loading, stretching, or further work. Contact a veterinarian promptly and describe the exercise, onset, sweating, stiffness, drinking, and urine changes. Follow advice about access to water, feed, transport, and medication; do not give human pain medicine. A veterinarian may examine muscle function and hydration and use blood or urine tests to judge muscle injury and kidney strain.

Treat sudden severe stiffness, collapse, repeated attempts to lie down, extreme sweating, weakness, or inability to move as urgent. Reduced urination, dark urine, dehydration, or signs of distress also warrant immediate veterinary help. Do not assume the episode is ordinary post-exercise soreness, especially when the horse cannot take comfortable steps.

Ask what tests are needed, how movement should be restricted, what diet and exercise changes may reduce recurrence, and which warning signs should trigger another call. Keep a record of episodes, workload, feed changes, and recovery.